Plate Nº 52 · recorded November 15, 2026
PhysicsReported finding
Physicists Spot Ultra-Rare Particle Decay After 40-Year Hunt
After 40 years of searching, CERN's upgraded LHCb experiment has evidence of a decay occurring once per 10 billion beauty particles, matching Standard Model predictions.
By Elena Vasquez4 min read818 words
In brief
- First evidence of the Bd to mu mu decay after more than 40 years of searching, recorded by the upgraded LHCb detector at CERN.
- The decay occurs roughly once in every 10 billion beauty particles; the signal carries 3.2 sigma significance, below the 5-sigma discovery threshold.
- The UK-built Vertex Locator sits 5 millimeters from the LHC beams; nearly 90 UK companies helped construct the detector.
- The upgraded experiment collects data at up to five times its previous rate, with a further upgrade planned to raise that tenfold.
- The LHCb upgrade was a 15-year project by a roughly 1,900-member international collaboration, with the UK making the largest national contribution.
Physicists have detected the first evidence of a particle decay that occurs only about once in every 10 billion beauty particles — after more than 40 years of searching. The signal came from the upgraded LHCb experiment at CERN's Large Hadron Collider, and it gives scientists a fresh way to test whether undiscovered particles are hiding beyond physics' best current theory.
The decay, known as Bd to mu mu, involves a particle containing a beauty quark transforming into two muons — heavier cousins of electrons. The statistical significance is 3.2 sigma, strong enough to count as evidence but short of the five-sigma bar particle physics requires for an official discovery. More data will decide.
What makes this decay so special?
Beauty quarks are heavy relatives of the up and down quarks that sit inside protons and neutrons. The LHC produces them in huge numbers when particles collide. They live for only about one and a half trillionths of a second before decaying.
The extreme rarity of this particular decay is exactly why physicists want it. An undiscovered particle could subtly shift the odds of a beauty particle decaying a given way, even if that particle never shows up directly in the detector. The rarer the decay, the more sensitive it is to such hidden influences.
Professor Chris Parkes, head of the Department of Physics and Astronomy at the University of Manchester, put the odds in human terms: "This decay is remarkably unlikely, the chance of it happening is roughly like going on a romantic date and, on your very first try, finding the one perfect match for you among everyone on Earth."
So far, the measurement matches the Standard Model — the field's best theory of fundamental particles and their interactions. That agreement is itself informative. Greater precision could reveal where the theory eventually breaks down.
What is the 'Zeptoverse'?
Researchers call their next target the "Zeptoverse" — an unexplored realm at distances of a zeptometer, a billionth of a trillionth of a meter. Unknown particles and forces may lurk there, and rare-decay measurements are one of the few ways to probe that scale.
Professor Conor Fitzpatrick of the University of Manchester, deputy physics coordinator of the international LHCb collaboration, said: "There has been a more than forty year long search by physicists worldwide to observe this decay. It is a golden channel to observe the effects of new physics from beyond our current knowledge."
He added: "The results from this experiment are expanding our understanding of nature at its most fundamental level. We are excited to have finally seen this elusive signal and looking forward to the future discoveries that will come from our data."
How did they catch it?
The key instrument is the Vertex Locator, a silicon pixel detector sitting just five millimeters — about 0.2 inches — from the LHC beams. Built largely in the UK, it tracks particle paths from collisions with extreme precision. University of Manchester researchers played central roles in the experiment and its upgrade.
Dr. Stefano De Capua, who led detector construction at Manchester, said: "We worked with nearly 90 UK companies to construct this detector and trained the next generation of scientists and engineers on the novel technologies we are using. It is these detectors that we use to locate where the beauty meson was produced and pinpoint where it decayed into two muons."
Parkes led the international LHCb collaboration through the upgrade's construction and its approval of the new result. He was made a Fellow of the Royal Society earlier this year for his LHCb work.
"The upgraded LHCb was a major undertaking — a fifteen-year design and construction project from a 1900 international member collaboration," Parkes said. "The UK made the largest nation contribution to the project, pioneering new technologies that have made today's result possible, where we probe nature at a new scale."
What comes next?
The upgraded experiment now collects data at up to five times its previous rate and should keep building a much larger dataset into the early 2030s. A further planned upgrade could raise that rate by another factor of ten, sharpening measurements and extending sensitivity to even shorter distances.
Parkes said plans are already underway for an experiment to exploit the next-generation High Luminosity LHC, probing physics at an even smaller scale.
Professor Brian Cox, a Manchester particle physicist not involved in the experiment, welcomed the result: "We upgrade our instruments and we see nature in greater detail. Occasionally we see something we don't understand, and then progress is made. We cannot know whether this progress will be incremental or genuinely world-changing — that's science! LHCb is a major scientific success."
The work is funded by the Science and Technology Facilities Council, part of UK Research and Innovation. For now, the tally is one elusive signal spotted — and a long runway of data still to come.
via google.com (Original)
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Correspondent covering money, funding and market shifts around general science news at SciBeat.
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